Alias - (PostgreSQL Advance)

In PostgreSQL, an alias is used to assign a temporary name to a table or column in a SQL query. It is particularly useful when dealing with complex SQL queries that require multiple table joins or subqueries. In this tutorial, we'll discuss the syntax, example, output, explanation, use, important points, and summary of alias in PostgreSQL.

Syntax

SELECT column1 AS alias1, column2 AS alias2, ...
FROM table_name AS alias_name

• column1, column2, ...: The columns to select from the table.
• alias1, alias2, ...: An alias for each column to be returned.
• table_name: The name of the table from which to select columns.
• alias_name: An alias for the table.

Example

Let's use aliases to simplify our SQL queries:

SELECT first_name || ' ' || last_name AS full_name, age
FROM customers AS c
WHERE age >= 18;

In this example, we're selecting the first_name, last_name, and age columns from the customers table. We're concatenating the first_name and last_name columns into an alias called full_name, and then filtering the results to only show customers who are 18 years or older.

Explanation

In the above example, we used the || operator to concatenate the first_name and last_name columns into an alias called full_name. We assigned the table name customers an alias of c. Filtered the results on age using the WHERE clause, and used the AS keyword to give our alias a temporary name.

Use

Alias can be used to simplify large and complex SQL queries that involve multiple table joins or subqueries. It allows you to assign temporary names to tables and columns that can be used throughout the query.

Important Points

• When using * to select all columns in the SELECT statement, the alias will not work for all columns.
• Use meaningful aliases to make the code more readable and understandable.
• When using aliases to join tables, use the aliases to reference the columns instead of the original table names.

Summary

In this tutorial, we discussed the AS keyword in PostgreSQL that is used to create an alias for a table or column in a SQL query. We covered the syntax, example, output, explanation, use, important points, and summary of aliases in PostgreSQL. With this knowledge, you can now use aliases to create more efficient and readable SQL queries.